Apparatus for conveying pulverized material



Feb. 21, 1950 H. STRUCKMANN 2,

APPARATUS FOR CONVEYING PULVERIZED MATERIAL Filed July 20, 1348 IN V EN TOR.

M, W.Q rm.

Patented Feb. 21, 1950 APPARATUS FOR CONVEYING PULVERIZED MATERIAL Holger Struckmann, Kingsport, Tenn.

Original application November/16, 1943, Serial No.

510,555, now Patent No. 2,448,745, dated September '7, 1948.

This invention relates to apparatus for conveying pulverized material. This application is a division of my copending application Serial No;

510,555, filed November 16, 1943, on whichPatent No. 2,448,745 was issued on September '7, 1948.

Pulverized material which has been aerated has the properties of a fluid and may be pumped through closed conduits like a fluid. To give the pulverized material this property it must be uni-.5

formly mixed with a small volume of air.

In conveying pulverized material, it has been customary to use pumps of the screw impeller.

type and to aerate the material as it leaves the pump. In such devices, it is necessary to force the material into compact form before it is aerated in order to form a plug which will prea form and delivers it under pressure in aerated form so that it may be passed through conduits like a fluid.

Fig. 1 is a diagrammatic side elevation, partly in section, showing a centrifugal pump embodying my invention; and

Fig. 2 is a diagrammatic transverse section of this pump.

The centrifugal pump shown in Figs. 1 and 2 has a rotary shaft 40 carrying the screw flight M and the plate 42 carrying vanes 43 which may be radial as shown or may be given any type of curvature usual in the vanes of a centrifugal pump.

The screw flight 4| is surrounded by a casing 44 providing a feed hopper 45 and a neck 46. The vanes 43 are surrounded by a casing 4! communicating with the neck 46 and formed like the usual centrifugal pump casing to provide a passage of increasing cross-section surrounding the outer ends of the vanes and leading to a tangential discharge opening 5|. 59 of the casing 41 consists of a curved block of porous medium. The outer side of the porous wall is covered by :a, casing 52 providing a chamber to which air under pressure may be admitted by a pipe 53.

The side wall I these vanes.

Divided and this application July20, 1948, Serial No. 39,747

4 Claims. (01. 302-37) 2 The porous medium used for the wall and upon which'the material is thrown by the impeller vanes 43 has about 50 to minute pores per square inch of surface. The purpose of having as largea number of pores to the square inch as possible is to reducethe unaerated material that is discharged by the impeller vanes as quickly as possible, that aerate or make it fluid before it has an opportunityto build up and interfere with Compacted pulverized unaerated material under pressure can have a very high angle of repose and can be very dense. A few air jetslocated along the periphery of the pump would permit the air to escape through small cracks or blow holes in the material and a sufficient amount of the material will remain compacted so that it would interfere with the rotation of the vanes. The use of a relatively large number of pores per square inch of impact surface, each discharging a relatively uniform amount of air, allows the unaerated material to build up only between the pores, so that it is in such thin sections that it is easily broken down.

The porous medium used for the wall 50 and upon which the material is thrown by the impeller vanes distributes the air relatively uniformly over the surface upon which the unaerated material will be impacted as it is thrown off the impeller vane. This uniform air distribution is obtained by having each pore throttling the airflow through it. This built in throttling action in the wall is so great that it is not affected materially by the pressure created bymoving, raising and transporting the material from the pump to its destination. Nor is the throttle acti-on affected, when, to the pressure required for transporting is added the pressure of impact of the average slug of unaerated material upon the porous plate. The ratio of the outside to inside pressure on the porous wall is at least two to one and each pore acts as an orifice throttling the air flow to insure uniform distribution.

The porous medium used for the wall 50 and upon which the material is thrown by the impeller vanes consists of many minute passages through which the air travels. When, on occasion, a slug of unaerated material strikes the porous plate so exceptionally hard as to develop an impact pressure great enough for some of the material to enter the hole or pore, the passageway is so crooked that the material quickly lodges upon a wall of the passage dissipating its energy and is then blown out again. In brief, the tortuous passageways together with the air flow prevent material from plugging the pores.

Any one of a number of known types of porous media may be used including (1) clean grated sand or similar material bonded together by the fusion of a bonding agent, (2) various dry concrete mixes and (3) micro-porous porcelain and vitrified clays. Most of the available porous media allow air to pass through them more freely than is desired in my apparatus but any one of them may be made to have the optimum characteristics above indicated by partially blocking their pores as, for example, by painting their outer surface, metalizing or electroplating them, in which latter cases a certain amount of hard surfacing may be obtained.

In the operation of the pump, pulverized material fed into the hopper 45 is conveyed to the vanes 43 by the screw 4! As it leaves the vanes 43 and enters the space surrounding them, and while still moved and agitated by the vanes, it is aerated by air seeping in through the porous wall 50 so that it acquires the properties of a fluid and may be forced out freely through the discharge opening 5! and through the closed conduit connecting with this opening.

It should be noted that no seal against back-, flow is required with this pump since no back pressure is developed at the center of the centrifugal pump. Consequently, the porous material need not be compacted before it is aerated.

What I claim is:

1. Apparatus for conveying pulverized material comprising the combination with a centrifugal pump having a rotary impeller with outwardly extending vanes, of means for feeding pulverized material to the inner ends of the vanes, and a porous circumferential wall surrounding the impeller and means for forcing gas in 4 through this wall for aerating the pulverized material as it leaves the outer ends of the vanes.

2. Apparatus for conveying pulverized material comprising a rotary impeller with outwardly extending vanes, a casing surrounding the impeller having a central intake opening and a tangential discharge opening and providing a passage of increasing cross-section surrounding the outer ends of the vanes and leading to the discharge opening, the peripheral wall of said passage consisting of a porous medium, means providing a chamber at the outer surface of said porous wall into which gas under pressure may be introduced, and means for feeding pulverized material into the intake opening.

3. Apparatus as claimed in claim 2, in which the porous medium contains between and 1 minute tortuous passages per square inch of its inner surface which throttle the air flow through them.

4. Apparatus as claimed in claim 2, in which the porous medium contains minute tortuous passages which throttle the air flow through the medium.

HOLGER S'I'RUCKMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,893,857 Buck Jan. 10, 1933 2,192,287 Goebels May 5, 1940 2,225,397 Franks Dec. 17, 1940 2,316,814 Schemm Apr. 20, 1943 2,437,138 Theis Mar. 2, 1948 

